/* * Copyright (C) 2015 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #include "induction_var_range.h" #include <limits> namespace art { /** Returns true if 64-bit constant fits in 32-bit constant. */ static bool CanLongValueFitIntoInt(int64_t c) { return std::numeric_limits<int32_t>::min() <= c && c <= std::numeric_limits<int32_t>::max(); } /** Returns true if 32-bit addition can be done safely. */ static bool IsSafeAdd(int32_t c1, int32_t c2) { return CanLongValueFitIntoInt(static_cast<int64_t>(c1) + static_cast<int64_t>(c2)); } /** Returns true if 32-bit subtraction can be done safely. */ static bool IsSafeSub(int32_t c1, int32_t c2) { return CanLongValueFitIntoInt(static_cast<int64_t>(c1) - static_cast<int64_t>(c2)); } /** Returns true if 32-bit multiplication can be done safely. */ static bool IsSafeMul(int32_t c1, int32_t c2) { return CanLongValueFitIntoInt(static_cast<int64_t>(c1) * static_cast<int64_t>(c2)); } /** Returns true if 32-bit division can be done safely. */ static bool IsSafeDiv(int32_t c1, int32_t c2) { return c2 != 0 && CanLongValueFitIntoInt(static_cast<int64_t>(c1) / static_cast<int64_t>(c2)); } /** Returns true for 32/64-bit constant instruction. */ static bool IsIntAndGet(HInstruction* instruction, int64_t* value) { if (instruction->IsIntConstant()) { *value = instruction->AsIntConstant()->GetValue(); return true; } else if (instruction->IsLongConstant()) { *value = instruction->AsLongConstant()->GetValue(); return true; } return false; } /** * An upper bound a * (length / a) + b, where a >= 1, can be conservatively rewritten as length + b * because length >= 0 is true. This makes it more likely the bound is useful to clients. */ static InductionVarRange::Value SimplifyMax(InductionVarRange::Value v) { int64_t value; if (v.is_known && v.a_constant >= 1 && v.instruction->IsDiv() && v.instruction->InputAt(0)->IsArrayLength() && IsIntAndGet(v.instruction->InputAt(1), &value) && v.a_constant == value) { return InductionVarRange::Value(v.instruction->InputAt(0), 1, v.b_constant); } return v; } /** * Corrects a value for type to account for arithmetic wrap-around in lower precision. */ static InductionVarRange::Value CorrectForType(InductionVarRange::Value v, Primitive::Type type) { switch (type) { case Primitive::kPrimShort: case Primitive::kPrimChar: case Primitive::kPrimByte: { // Constants within range only. // TODO: maybe some room for improvement, like allowing widening conversions const int32_t min = Primitive::MinValueOfIntegralType(type); const int32_t max = Primitive::MaxValueOfIntegralType(type); return (v.is_known && v.a_constant == 0 && min <= v.b_constant && v.b_constant <= max) ? v : InductionVarRange::Value(); } default: // At int or higher. return v; } } /** Helper method to test for a constant value. */ static bool IsConstantValue(InductionVarRange::Value v) { return v.is_known && v.a_constant == 0; } /** Helper method to test for same constant value. */ static bool IsSameConstantValue(InductionVarRange::Value v1, InductionVarRange::Value v2) { return IsConstantValue(v1) && IsConstantValue(v2) && v1.b_constant == v2.b_constant; } /** Helper method to insert an instruction. */ static HInstruction* Insert(HBasicBlock* block, HInstruction* instruction) { DCHECK(block != nullptr); DCHECK(block->GetLastInstruction() != nullptr) << block->GetBlockId(); DCHECK(instruction != nullptr); block->InsertInstructionBefore(instruction, block->GetLastInstruction()); return instruction; } // // Public class methods. // InductionVarRange::InductionVarRange(HInductionVarAnalysis* induction_analysis) : induction_analysis_(induction_analysis) { DCHECK(induction_analysis != nullptr); } bool InductionVarRange::GetInductionRange(HInstruction* context, HInstruction* instruction, /*out*/Value* min_val, /*out*/Value* max_val, /*out*/bool* needs_finite_test) { HLoopInformation* loop = context->GetBlock()->GetLoopInformation(); // closest enveloping loop if (loop == nullptr) { return false; // no loop } HInductionVarAnalysis::InductionInfo* info = induction_analysis_->LookupInfo(loop, instruction); if (info == nullptr) { return false; // no induction information } // Type int or lower (this is not too restrictive since intended clients, like // bounds check elimination, will have truncated higher precision induction // at their use point already). switch (info->type) { case Primitive::kPrimInt: case Primitive::kPrimShort: case Primitive::kPrimChar: case Primitive::kPrimByte: break; default: return false; } // Set up loop information. HBasicBlock* header = loop->GetHeader(); bool in_body = context->GetBlock() != header; HInductionVarAnalysis::InductionInfo* trip = induction_analysis_->LookupInfo(loop, header->GetLastInstruction()); // Find range. *min_val = GetVal(info, trip, in_body, /* is_min */ true); *max_val = SimplifyMax(GetVal(info, trip, in_body, /* is_min */ false)); *needs_finite_test = NeedsTripCount(info) && IsUnsafeTripCount(trip); return true; } bool InductionVarRange::RefineOuter(/*in-out*/ Value* min_val, /*in-out*/ Value* max_val) const { if (min_val->instruction != nullptr || max_val->instruction != nullptr) { Value v1_min = RefineOuter(*min_val, /* is_min */ true); Value v2_max = RefineOuter(*max_val, /* is_min */ false); // The refined range is safe if both sides refine the same instruction. Otherwise, since two // different ranges are combined, the new refined range is safe to pass back to the client if // the extremes of the computed ranges ensure no arithmetic wrap-around anomalies occur. if (min_val->instruction != max_val->instruction) { Value v1_max = RefineOuter(*min_val, /* is_min */ false); Value v2_min = RefineOuter(*max_val, /* is_min */ true); if (!IsConstantValue(v1_max) || !IsConstantValue(v2_min) || v1_max.b_constant > v2_min.b_constant) { return false; } } // Did something change? if (v1_min.instruction != min_val->instruction || v2_max.instruction != max_val->instruction) { *min_val = v1_min; *max_val = v2_max; return true; } } return false; } bool InductionVarRange::CanGenerateCode(HInstruction* context, HInstruction* instruction, /*out*/bool* needs_finite_test, /*out*/bool* needs_taken_test) { return GenerateCode(context, instruction, nullptr, nullptr, nullptr, nullptr, nullptr, // nothing generated yet needs_finite_test, needs_taken_test); } void InductionVarRange::GenerateRangeCode(HInstruction* context, HInstruction* instruction, HGraph* graph, HBasicBlock* block, /*out*/HInstruction** lower, /*out*/HInstruction** upper) { bool b1, b2; // unused if (!GenerateCode(context, instruction, graph, block, lower, upper, nullptr, &b1, &b2)) { LOG(FATAL) << "Failed precondition: GenerateCode()"; } } void InductionVarRange::GenerateTakenTest(HInstruction* context, HGraph* graph, HBasicBlock* block, /*out*/HInstruction** taken_test) { bool b1, b2; // unused if (!GenerateCode(context, context, graph, block, nullptr, nullptr, taken_test, &b1, &b2)) { LOG(FATAL) << "Failed precondition: GenerateCode()"; } } // // Private class methods. // bool InductionVarRange::IsConstant(HInductionVarAnalysis::InductionInfo* info, ConstantRequest request, /*out*/ int64_t *value) const { if (info != nullptr) { // A direct 32-bit or 64-bit constant fetch. This immediately satisfies // any of the three requests (kExact, kAtMost, and KAtLeast). if (info->induction_class == HInductionVarAnalysis::kInvariant && info->operation == HInductionVarAnalysis::kFetch) { if (IsIntAndGet(info->fetch, value)) { return true; } } // Try range analysis while traversing outward on loops. bool in_body = true; // no known trip count Value v_min = GetVal(info, nullptr, in_body, /* is_min */ true); Value v_max = GetVal(info, nullptr, in_body, /* is_min */ false); do { // Make sure *both* extremes are known to avoid arithmetic wrap-around anomalies. if (IsConstantValue(v_min) && IsConstantValue(v_max) && v_min.b_constant <= v_max.b_constant) { if ((request == kExact && v_min.b_constant == v_max.b_constant) || request == kAtMost) { *value = v_max.b_constant; return true; } else if (request == kAtLeast) { *value = v_min.b_constant; return true; } } } while (RefineOuter(&v_min, &v_max)); // Exploit array length + c >= c, with c <= 0 to avoid arithmetic wrap-around anomalies // (e.g. array length == maxint and c == 1 would yield minint). if (request == kAtLeast) { if (v_min.a_constant == 1 && v_min.b_constant <= 0 && v_min.instruction->IsArrayLength()) { *value = v_min.b_constant; return true; } } } return false; } bool InductionVarRange::NeedsTripCount(HInductionVarAnalysis::InductionInfo* info) const { if (info != nullptr) { if (info->induction_class == HInductionVarAnalysis::kLinear) { return true; } else if (info->induction_class == HInductionVarAnalysis::kWrapAround) { return NeedsTripCount(info->op_b); } } return false; } bool InductionVarRange::IsBodyTripCount(HInductionVarAnalysis::InductionInfo* trip) const { if (trip != nullptr) { if (trip->induction_class == HInductionVarAnalysis::kInvariant) { return trip->operation == HInductionVarAnalysis::kTripCountInBody || trip->operation == HInductionVarAnalysis::kTripCountInBodyUnsafe; } } return false; } bool InductionVarRange::IsUnsafeTripCount(HInductionVarAnalysis::InductionInfo* trip) const { if (trip != nullptr) { if (trip->induction_class == HInductionVarAnalysis::kInvariant) { return trip->operation == HInductionVarAnalysis::kTripCountInBodyUnsafe || trip->operation == HInductionVarAnalysis::kTripCountInLoopUnsafe; } } return false; } InductionVarRange::Value InductionVarRange::GetLinear(HInductionVarAnalysis::InductionInfo* info, HInductionVarAnalysis::InductionInfo* trip, bool in_body, bool is_min) const { // Detect common situation where an offset inside the trip count cancels out during range // analysis (finding max a * (TC - 1) + OFFSET for a == 1 and TC = UPPER - OFFSET or finding // min a * (TC - 1) + OFFSET for a == -1 and TC = OFFSET - UPPER) to avoid losing information // with intermediate results that only incorporate single instructions. if (trip != nullptr) { HInductionVarAnalysis::InductionInfo* trip_expr = trip->op_a; if (trip_expr->operation == HInductionVarAnalysis::kSub) { int64_t stride_value = 0; if (IsConstant(info->op_a, kExact, &stride_value)) { if (!is_min && stride_value == 1) { // Test original trip's negative operand (trip_expr->op_b) against offset of induction. if (HInductionVarAnalysis::InductionEqual(trip_expr->op_b, info->op_b)) { // Analyze cancelled trip with just the positive operand (trip_expr->op_a). HInductionVarAnalysis::InductionInfo cancelled_trip( trip->induction_class, trip->operation, trip_expr->op_a, trip->op_b, nullptr, trip->type); return GetVal(&cancelled_trip, trip, in_body, is_min); } } else if (is_min && stride_value == -1) { // Test original trip's positive operand (trip_expr->op_a) against offset of induction. if (HInductionVarAnalysis::InductionEqual(trip_expr->op_a, info->op_b)) { // Analyze cancelled trip with just the negative operand (trip_expr->op_b). HInductionVarAnalysis::InductionInfo neg( HInductionVarAnalysis::kInvariant, HInductionVarAnalysis::kNeg, nullptr, trip_expr->op_b, nullptr, trip->type); HInductionVarAnalysis::InductionInfo cancelled_trip( trip->induction_class, trip->operation, &neg, trip->op_b, nullptr, trip->type); return SubValue(Value(0), GetVal(&cancelled_trip, trip, in_body, !is_min)); } } } } } // General rule of linear induction a * i + b, for normalized 0 <= i < TC. return AddValue(GetMul(info->op_a, trip, trip, in_body, is_min), GetVal(info->op_b, trip, in_body, is_min)); } InductionVarRange::Value InductionVarRange::GetFetch(HInstruction* instruction, HInductionVarAnalysis::InductionInfo* trip, bool in_body, bool is_min) const { // Detect constants and chase the fetch a bit deeper into the HIR tree, so that it becomes // more likely range analysis will compare the same instructions as terminal nodes. int64_t value; if (IsIntAndGet(instruction, &value) && CanLongValueFitIntoInt(value)) { return Value(static_cast<int32_t>(value)); } else if (instruction->IsAdd()) { if (IsIntAndGet(instruction->InputAt(0), &value) && CanLongValueFitIntoInt(value)) { return AddValue(Value(static_cast<int32_t>(value)), GetFetch(instruction->InputAt(1), trip, in_body, is_min)); } else if (IsIntAndGet(instruction->InputAt(1), &value) && CanLongValueFitIntoInt(value)) { return AddValue(GetFetch(instruction->InputAt(0), trip, in_body, is_min), Value(static_cast<int32_t>(value))); } } else if (instruction->IsArrayLength() && instruction->InputAt(0)->IsNewArray()) { return GetFetch(instruction->InputAt(0)->InputAt(0), trip, in_body, is_min); } else if (instruction->IsTypeConversion()) { // Since analysis is 32-bit (or narrower) we allow a widening along the path. if (instruction->AsTypeConversion()->GetInputType() == Primitive::kPrimInt && instruction->AsTypeConversion()->GetResultType() == Primitive::kPrimLong) { return GetFetch(instruction->InputAt(0), trip, in_body, is_min); } } else if (is_min) { // Special case for finding minimum: minimum of trip-count in loop-body is 1. if (trip != nullptr && in_body && instruction == trip->op_a->fetch) { return Value(1); } } return Value(instruction, 1, 0); } InductionVarRange::Value InductionVarRange::GetVal(HInductionVarAnalysis::InductionInfo* info, HInductionVarAnalysis::InductionInfo* trip, bool in_body, bool is_min) const { if (info != nullptr) { switch (info->induction_class) { case HInductionVarAnalysis::kInvariant: // Invariants. switch (info->operation) { case HInductionVarAnalysis::kAdd: return AddValue(GetVal(info->op_a, trip, in_body, is_min), GetVal(info->op_b, trip, in_body, is_min)); case HInductionVarAnalysis::kSub: // second reversed! return SubValue(GetVal(info->op_a, trip, in_body, is_min), GetVal(info->op_b, trip, in_body, !is_min)); case HInductionVarAnalysis::kNeg: // second reversed! return SubValue(Value(0), GetVal(info->op_b, trip, in_body, !is_min)); case HInductionVarAnalysis::kMul: return GetMul(info->op_a, info->op_b, trip, in_body, is_min); case HInductionVarAnalysis::kDiv: return GetDiv(info->op_a, info->op_b, trip, in_body, is_min); case HInductionVarAnalysis::kFetch: return GetFetch(info->fetch, trip, in_body, is_min); case HInductionVarAnalysis::kTripCountInLoop: case HInductionVarAnalysis::kTripCountInLoopUnsafe: if (!in_body && !is_min) { // one extra! return GetVal(info->op_a, trip, in_body, is_min); } FALLTHROUGH_INTENDED; case HInductionVarAnalysis::kTripCountInBody: case HInductionVarAnalysis::kTripCountInBodyUnsafe: if (is_min) { return Value(0); } else if (in_body) { return SubValue(GetVal(info->op_a, trip, in_body, is_min), Value(1)); } break; default: break; } break; case HInductionVarAnalysis::kLinear: { return CorrectForType(GetLinear(info, trip, in_body, is_min), info->type); } case HInductionVarAnalysis::kWrapAround: case HInductionVarAnalysis::kPeriodic: return MergeVal(GetVal(info->op_a, trip, in_body, is_min), GetVal(info->op_b, trip, in_body, is_min), is_min); } } return Value(); } InductionVarRange::Value InductionVarRange::GetMul(HInductionVarAnalysis::InductionInfo* info1, HInductionVarAnalysis::InductionInfo* info2, HInductionVarAnalysis::InductionInfo* trip, bool in_body, bool is_min) const { Value v1_min = GetVal(info1, trip, in_body, /* is_min */ true); Value v1_max = GetVal(info1, trip, in_body, /* is_min */ false); Value v2_min = GetVal(info2, trip, in_body, /* is_min */ true); Value v2_max = GetVal(info2, trip, in_body, /* is_min */ false); // Try to refine first operand. if (!IsConstantValue(v1_min) && !IsConstantValue(v1_max)) { RefineOuter(&v1_min, &v1_max); } // Constant times range. if (IsSameConstantValue(v1_min, v1_max)) { return MulRangeAndConstant(v2_min, v2_max, v1_min, is_min); } else if (IsSameConstantValue(v2_min, v2_max)) { return MulRangeAndConstant(v1_min, v1_max, v2_min, is_min); } // Positive range vs. positive or negative range. if (IsConstantValue(v1_min) && v1_min.b_constant >= 0) { if (IsConstantValue(v2_min) && v2_min.b_constant >= 0) { return is_min ? MulValue(v1_min, v2_min) : MulValue(v1_max, v2_max); } else if (IsConstantValue(v2_max) && v2_max.b_constant <= 0) { return is_min ? MulValue(v1_max, v2_min) : MulValue(v1_min, v2_max); } } // Negative range vs. positive or negative range. if (IsConstantValue(v1_max) && v1_max.b_constant <= 0) { if (IsConstantValue(v2_min) && v2_min.b_constant >= 0) { return is_min ? MulValue(v1_min, v2_max) : MulValue(v1_max, v2_min); } else if (IsConstantValue(v2_max) && v2_max.b_constant <= 0) { return is_min ? MulValue(v1_max, v2_max) : MulValue(v1_min, v2_min); } } return Value(); } InductionVarRange::Value InductionVarRange::GetDiv(HInductionVarAnalysis::InductionInfo* info1, HInductionVarAnalysis::InductionInfo* info2, HInductionVarAnalysis::InductionInfo* trip, bool in_body, bool is_min) const { Value v1_min = GetVal(info1, trip, in_body, /* is_min */ true); Value v1_max = GetVal(info1, trip, in_body, /* is_min */ false); Value v2_min = GetVal(info2, trip, in_body, /* is_min */ true); Value v2_max = GetVal(info2, trip, in_body, /* is_min */ false); // Range divided by constant. if (IsSameConstantValue(v2_min, v2_max)) { return DivRangeAndConstant(v1_min, v1_max, v2_min, is_min); } // Positive range vs. positive or negative range. if (IsConstantValue(v1_min) && v1_min.b_constant >= 0) { if (IsConstantValue(v2_min) && v2_min.b_constant >= 0) { return is_min ? DivValue(v1_min, v2_max) : DivValue(v1_max, v2_min); } else if (IsConstantValue(v2_max) && v2_max.b_constant <= 0) { return is_min ? DivValue(v1_max, v2_max) : DivValue(v1_min, v2_min); } } // Negative range vs. positive or negative range. if (IsConstantValue(v1_max) && v1_max.b_constant <= 0) { if (IsConstantValue(v2_min) && v2_min.b_constant >= 0) { return is_min ? DivValue(v1_min, v2_min) : DivValue(v1_max, v2_max); } else if (IsConstantValue(v2_max) && v2_max.b_constant <= 0) { return is_min ? DivValue(v1_max, v2_min) : DivValue(v1_min, v2_max); } } return Value(); } InductionVarRange::Value InductionVarRange::MulRangeAndConstant(Value v_min, Value v_max, Value c, bool is_min) const { return is_min == (c.b_constant >= 0) ? MulValue(v_min, c) : MulValue(v_max, c); } InductionVarRange::Value InductionVarRange::DivRangeAndConstant(Value v_min, Value v_max, Value c, bool is_min) const { return is_min == (c.b_constant >= 0) ? DivValue(v_min, c) : DivValue(v_max, c); } InductionVarRange::Value InductionVarRange::AddValue(Value v1, Value v2) const { if (v1.is_known && v2.is_known && IsSafeAdd(v1.b_constant, v2.b_constant)) { const int32_t b = v1.b_constant + v2.b_constant; if (v1.a_constant == 0) { return Value(v2.instruction, v2.a_constant, b); } else if (v2.a_constant == 0) { return Value(v1.instruction, v1.a_constant, b); } else if (v1.instruction == v2.instruction && IsSafeAdd(v1.a_constant, v2.a_constant)) { return Value(v1.instruction, v1.a_constant + v2.a_constant, b); } } return Value(); } InductionVarRange::Value InductionVarRange::SubValue(Value v1, Value v2) const { if (v1.is_known && v2.is_known && IsSafeSub(v1.b_constant, v2.b_constant)) { const int32_t b = v1.b_constant - v2.b_constant; if (v1.a_constant == 0 && IsSafeSub(0, v2.a_constant)) { return Value(v2.instruction, -v2.a_constant, b); } else if (v2.a_constant == 0) { return Value(v1.instruction, v1.a_constant, b); } else if (v1.instruction == v2.instruction && IsSafeSub(v1.a_constant, v2.a_constant)) { return Value(v1.instruction, v1.a_constant - v2.a_constant, b); } } return Value(); } InductionVarRange::Value InductionVarRange::MulValue(Value v1, Value v2) const { if (v1.is_known && v2.is_known) { if (v1.a_constant == 0) { if (IsSafeMul(v1.b_constant, v2.a_constant) && IsSafeMul(v1.b_constant, v2.b_constant)) { return Value(v2.instruction, v1.b_constant * v2.a_constant, v1.b_constant * v2.b_constant); } } else if (v2.a_constant == 0) { if (IsSafeMul(v1.a_constant, v2.b_constant) && IsSafeMul(v1.b_constant, v2.b_constant)) { return Value(v1.instruction, v1.a_constant * v2.b_constant, v1.b_constant * v2.b_constant); } } } return Value(); } InductionVarRange::Value InductionVarRange::DivValue(Value v1, Value v2) const { if (v1.is_known && v2.is_known && v1.a_constant == 0 && v2.a_constant == 0) { if (IsSafeDiv(v1.b_constant, v2.b_constant)) { return Value(v1.b_constant / v2.b_constant); } } return Value(); } InductionVarRange::Value InductionVarRange::MergeVal(Value v1, Value v2, bool is_min) const { if (v1.is_known && v2.is_known) { if (v1.instruction == v2.instruction && v1.a_constant == v2.a_constant) { return Value(v1.instruction, v1.a_constant, is_min ? std::min(v1.b_constant, v2.b_constant) : std::max(v1.b_constant, v2.b_constant)); } } return Value(); } InductionVarRange::Value InductionVarRange::RefineOuter(Value v, bool is_min) const { if (v.instruction == nullptr) { return v; // nothing to refine } HLoopInformation* loop = v.instruction->GetBlock()->GetLoopInformation(); // closest enveloping loop if (loop == nullptr) { return v; // no loop } HInductionVarAnalysis::InductionInfo* info = induction_analysis_->LookupInfo(loop, v.instruction); if (info == nullptr) { return v; // no induction information } // Set up loop information. HBasicBlock* header = loop->GetHeader(); bool in_body = true; // inner always in more outer HInductionVarAnalysis::InductionInfo* trip = induction_analysis_->LookupInfo(loop, header->GetLastInstruction()); // Try to refine "a x instruction + b" with outer loop range information on instruction. return AddValue(MulValue(Value(v.a_constant), GetVal(info, trip, in_body, is_min)), Value(v.b_constant)); } bool InductionVarRange::GenerateCode(HInstruction* context, HInstruction* instruction, HGraph* graph, HBasicBlock* block, /*out*/HInstruction** lower, /*out*/HInstruction** upper, /*out*/HInstruction** taken_test, /*out*/bool* needs_finite_test, /*out*/bool* needs_taken_test) const { HLoopInformation* loop = context->GetBlock()->GetLoopInformation(); // closest enveloping loop if (loop == nullptr) { return false; // no loop } HInductionVarAnalysis::InductionInfo* info = induction_analysis_->LookupInfo(loop, instruction); if (info == nullptr) { return false; // no induction information } // Set up loop information. HBasicBlock* header = loop->GetHeader(); bool in_body = context->GetBlock() != header; HInductionVarAnalysis::InductionInfo* trip = induction_analysis_->LookupInfo(loop, header->GetLastInstruction()); if (trip == nullptr) { return false; // codegen relies on trip count } // Determine what tests are needed. A finite test is needed if the evaluation code uses the // trip-count and the loop maybe unsafe (because in such cases, the index could "overshoot" // the computed range). A taken test is needed for any unknown trip-count, even if evaluation // code does not use the trip-count explicitly (since there could be an implicit relation // between e.g. an invariant subscript and a not-taken condition). *needs_finite_test = NeedsTripCount(info) && IsUnsafeTripCount(trip); *needs_taken_test = IsBodyTripCount(trip); // Code generation for taken test: generate the code when requested or otherwise analyze // if code generation is feasible when taken test is needed. if (taken_test != nullptr) { return GenerateCode(trip->op_b, nullptr, graph, block, taken_test, in_body, /* is_min */ false); } else if (*needs_taken_test) { if (!GenerateCode( trip->op_b, nullptr, nullptr, nullptr, nullptr, in_body, /* is_min */ false)) { return false; } } // Code generation for lower and upper. return // Success on lower if invariant (not set), or code can be generated. ((info->induction_class == HInductionVarAnalysis::kInvariant) || GenerateCode(info, trip, graph, block, lower, in_body, /* is_min */ true)) && // And success on upper. GenerateCode(info, trip, graph, block, upper, in_body, /* is_min */ false); } bool InductionVarRange::GenerateCode(HInductionVarAnalysis::InductionInfo* info, HInductionVarAnalysis::InductionInfo* trip, HGraph* graph, // when set, code is generated HBasicBlock* block, /*out*/HInstruction** result, bool in_body, bool is_min) const { if (info != nullptr) { // Verify type safety. Primitive::Type type = Primitive::kPrimInt; if (info->type != type) { return false; } // Handle current operation. HInstruction* opa = nullptr; HInstruction* opb = nullptr; switch (info->induction_class) { case HInductionVarAnalysis::kInvariant: // Invariants. switch (info->operation) { case HInductionVarAnalysis::kAdd: case HInductionVarAnalysis::kLT: case HInductionVarAnalysis::kLE: case HInductionVarAnalysis::kGT: case HInductionVarAnalysis::kGE: if (GenerateCode(info->op_a, trip, graph, block, &opa, in_body, is_min) && GenerateCode(info->op_b, trip, graph, block, &opb, in_body, is_min)) { if (graph != nullptr) { HInstruction* operation = nullptr; switch (info->operation) { case HInductionVarAnalysis::kAdd: operation = new (graph->GetArena()) HAdd(type, opa, opb); break; case HInductionVarAnalysis::kLT: operation = new (graph->GetArena()) HLessThan(opa, opb); break; case HInductionVarAnalysis::kLE: operation = new (graph->GetArena()) HLessThanOrEqual(opa, opb); break; case HInductionVarAnalysis::kGT: operation = new (graph->GetArena()) HGreaterThan(opa, opb); break; case HInductionVarAnalysis::kGE: operation = new (graph->GetArena()) HGreaterThanOrEqual(opa, opb); break; default: LOG(FATAL) << "unknown operation"; } *result = Insert(block, operation); } return true; } break; case HInductionVarAnalysis::kSub: // second reversed! if (GenerateCode(info->op_a, trip, graph, block, &opa, in_body, is_min) && GenerateCode(info->op_b, trip, graph, block, &opb, in_body, !is_min)) { if (graph != nullptr) { *result = Insert(block, new (graph->GetArena()) HSub(type, opa, opb)); } return true; } break; case HInductionVarAnalysis::kNeg: // reversed! if (GenerateCode(info->op_b, trip, graph, block, &opb, in_body, !is_min)) { if (graph != nullptr) { *result = Insert(block, new (graph->GetArena()) HNeg(type, opb)); } return true; } break; case HInductionVarAnalysis::kFetch: if (graph != nullptr) { *result = info->fetch; // already in HIR } return true; case HInductionVarAnalysis::kTripCountInLoop: case HInductionVarAnalysis::kTripCountInLoopUnsafe: if (!in_body && !is_min) { // one extra! return GenerateCode(info->op_a, trip, graph, block, result, in_body, is_min); } FALLTHROUGH_INTENDED; case HInductionVarAnalysis::kTripCountInBody: case HInductionVarAnalysis::kTripCountInBodyUnsafe: if (is_min) { if (graph != nullptr) { *result = graph->GetIntConstant(0); } return true; } else if (in_body) { if (GenerateCode(info->op_a, trip, graph, block, &opb, in_body, is_min)) { if (graph != nullptr) { *result = Insert(block, new (graph->GetArena()) HSub(type, opb, graph->GetIntConstant(1))); } return true; } } break; default: break; } break; case HInductionVarAnalysis::kLinear: { // Linear induction a * i + b, for normalized 0 <= i < TC. Restrict to unit stride only // to avoid arithmetic wrap-around situations that are hard to guard against. int64_t stride_value = 0; if (IsConstant(info->op_a, kExact, &stride_value)) { if (stride_value == 1 || stride_value == -1) { const bool is_min_a = stride_value == 1 ? is_min : !is_min; if (GenerateCode(trip, trip, graph, block, &opa, in_body, is_min_a) && GenerateCode(info->op_b, trip, graph, block, &opb, in_body, is_min)) { if (graph != nullptr) { HInstruction* oper; if (stride_value == 1) { oper = new (graph->GetArena()) HAdd(type, opa, opb); } else { oper = new (graph->GetArena()) HSub(type, opb, opa); } *result = Insert(block, oper); } return true; } } } break; } case HInductionVarAnalysis::kWrapAround: case HInductionVarAnalysis::kPeriodic: { // Wrap-around and periodic inductions are restricted to constants only, so that extreme // values are easy to test at runtime without complications of arithmetic wrap-around. Value extreme = GetVal(info, trip, in_body, is_min); if (IsConstantValue(extreme)) { if (graph != nullptr) { *result = graph->GetIntConstant(extreme.b_constant); } return true; } break; } default: break; } } return false; } } // namespace art